1. Field of the Invention
This invention relates to an image recording method and apparatus for recording an image on a heat development photosensitive material. This invention particularly relates to a dry type of image recording method and apparatus for recording a medical image, which has multiple gradation levels, (i.e. a continuous tone medical image) on a heat development photosensitive material. Specifically, this invention relates to an image recording method and apparatus for developing a latent image, which has been formed on a heat development photosensitive material by a laser beam scanning operation, and thereby obtaining a medical image having multiple gradation levels.
2. Description of the Prior Art
As methods for recording an image having multiple gradation levels, such as a medical image, on a recording material, wet development recording methods utilizing silver halide photosensitive materials have heretofore been popular. However, in hospitals, and the like, where medical images are processed, from the view point of environmental protection, the wet development using large amounts of various chemicals has become increasingly unfavorable. Also, it is not easy to carry out the wet development. Therefore, nowadays there is a strong demand for dry types of recording methods. As one of the dry types of recording methods, electrophotography is known. However, the electrophotography has the problems with regard to reproduction of multiple gradation levels. At present, it is considered that the electrophotography cannot be easily used in practice for medical images.
Therefore, it is considered to employ a heat development technique, which is known as one of dry types of recording techniques. However, even if the heat development technique is merely utilized, practically satisfactory medical images having a high gradation accuracy and good image quality cannot be obtained.
For example, in order for development to be carried out quickly by shortening the processing time, the processing temperature may be set to be high. However, in cases where the processing temperature is set to be high, much noise occurs in the image. Therefore, an image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, cannot be obtained. In cases where the processing temperature is set to be low such that noise may be reduced and the image quality may be enhanced, a long processing time is required, and the processing efficiency cannot be kept high. In particular, as for a medical image, it is desired that the medical image has good image quality and can serve as an effective tool in the efficient and accurate diagnosis of an illness. In order for a medical image suitable for the practical use to be obtained with the heat development technique, various conditions must be taken into consideration.